Method of obtaining stereoscopic impressions of moving picture images



May 19, 1931 ARFSTEN 1,806,190-

METHOD OF OBTAINING STEREOSCOPIG IMPRESSIONS UF MOVING PICTURE IMAGESFiled Jan. 6, 1928 7 Sheets-Sheet 1 11': ATTORNEY.

May 19, 1931. N. ARFSTEN 1,806,190

METHOD OF OBTAINING STEREOSCOPIC IMPRESSIONS OF MOVING PICTURE IMAGESFiled Jan. 6, 1928 7 Sheets-Sheet 2 INVEN T OR.

11.; A TT ORNE Y.

May 19, 1931. N. ARFSTEN I 1,806,190

METHOD OF OBTAINING STEREOSCOPIC IMPRESSIONS OF MOVING PICTURE IMAGESFiled Jan. 6, 1928 7 Sheets-Sheet 3 i J F a v F J Z r 57 i 7 I l I] j 1I 9 20 I J/m 2" J2 :2) J j JJ [5n I52;

IN VEN TOR.

Z1 ATTORNEY.

RE IMAGES N. ARFSTEN May 19, 1931.

METHOD OF OBTA INING STEREOSCQPIC IMPRESSIONS OF MOVING PICTU Filed Jan.6, 1928 7 Sheets-Sheet 4 INVENTOR flaw #44 ATTORNEY.

Fig. 11

May 19, 1931. 'N. ARFSTEN 1,806,190

METHOD OF OBTAINING STEREOSCOPIC IMPRESSIONS OF MOVING PICTURE IMAGESFiled Jan. 6, 1928 7 Sheets-Sheet 5 Fig. /2

I INVENTOR.

Z1: A TTORNE Y.

N. ARFSTEN May 19, 1931.

Filed Jan. 6,. 1928 7 Sheets-Sheet 6 Fig. 16

H m w A L HYVEN TOR.

May 19, 1931. N. ARFSTEN 1,806,190

METHOD OF OBTAINING STEREOSCOPIC IMPRESSIONS OF MOVING PICTURE IMAGESFiled Jan. 6, 1928 7 Sheets-Sheet '7 ATTORNEY.

Patented May 19, 1931 P 1,806,190

UNITED STATES PATENT OFFICE NEWTON ARFS'IEN OF NEW YORK, N. Y.

METHOD OF OBTAINING STEREOSCOPIC IM PRESSIONS F MOVING PICTURE IMAGESApplication filed January 6, 1928. Serial No. 244,849.

This invention relates to a method of proother weaker impression whichotherwise jecting moving picture images to produce 2. might beperceived. From another aspect, threedimensional impression onobservers, my invention provides for an arrangement and to anarrangement and apparatus for which shields the non-seeing eye for thecarrying out the aforesaid method. proper intervals in a novel mannerwhich 55 A well. known method of producingathreedoes not involve theplacing of an object dimensional impression on observers is based suchas a rotary shutter or the like in front on the use of two stereopticalpictures, nameof the observers face or the provision of other ly, of aleft-eye picture and of a right-eye uncomfortable instrumentalities. Myinpicture. The left-eye picture represents that vention is based on thefact that the ability on view of an object which is seen with the leftof the one eye of perceiving or seeing a cereye, while the right-eyepicture represents the tain view remains unaffected by alight imviewsimultanenously received of the same pression created in the other eyeproviding object by the right eye. If the object is subthat such lightimpression is entirely unijected to variations, for instance to a moveform and homogeneous. I utilize further- 65 ment, both pictures must betaken simultanemore the fact that a sudden light such as a ous y. Inorder to produce the three-dimenflash or a short projection of a picturewill sional impression on an observer, either sterebe perceived by thehuman eye only after a optical picture must be individuallypresentcertain interval has elapsed. The length of 0 edto thecorresponding eye. It is not an abthis interval, i. e., the intervalbetween the 7 solute requirement, however, to present both actualemission of light rays and their rpictures simultaneously, but thedesired efception by the human eye and brain, wil be feet will also beobtained if both pictures are hereinafter referred to as perceptiontime. alternately seen by the observer in so rapid The same depends to alarge extent on the ina succession as to producea uniform imprestensityof the light projection. The stronger sion. In the case of a movingpicture, the the light, the shorter will be the perception right-eyeview and the left-eye view are protime. One and the same lightprojection apjected on the screen in alternation. In order pears in aless degree of brightness, if the 1 to produce a correctthree-dimensional imeye receives an additional light. This addipression,both projections must be so positional light may be thrown into the eyefrom tioned on the screen in relation to each other the side or fromsome other place surroundthat the representation of a relatively disingthe light projection. The stronger such tant object, such for instanceas a far ofi additional light is, the longer will be the mountain peak,will appear on the screen in perception time of the light projection;Un-

5 the left-eye projection about 2 inches left der the condition that theadditional light apfrom the representation of this object in the pearsin a certain (red) color, only the perright-eye picture, the distance of2% inches ception time of the same (red) colored light being the averagedistance between the eyes. will be prolongated and the perception timeIt is obvious that in the case of alternative of the contrasting (green)light will be of a 40 projections, while the one eye is receiving anshorter endurance. impression, the other eye must be shielded or A lightprojection in a darkened room will otherwise protected from receivingimpresbe perceived by'the human eye only, after sions interfering withthe observation. a long perception time, if the eye is in a state Myinvention relates to a novel way of preof adaptation such as created bythe day- 45 venting the one eye from seeing while the light. But stayingin the darkened room, the other eye receives a picture impression, andperception time gradually becomes shorter consists in producing in theeye to be shieldand shorter until a certain point is attained. ed auniform, homogeneous light impression At this point, which will behereinafter rewhich is free from marked or conspicuous 'ferred to ascritical state the perception 50 points, and is so strong as toextinguish any time is suddenly prolongated for a. little 19.

while." Passing this" critical state the per ception time again becomesshorter and shorter until the eye receives its greatest sensibilitywhich the perception time of a blue light is in the socalled state ofdark-adaptation. vAs

during the expiration of the state of adaptation created by day-lightand that of darkadaptation the critical state of a. blue light appearspreviously to the other colors, of which the red oneis the last, it ispossible to accomplish a certain state of adaptation durin which theperception time of a red light is shorter than that of a blue one andanother certain state of adaptation during shorter than that of a redone.

Various embodiments of my invention are illustrated in the accompanyingdrawings.

Fig. 1 shows a plan view of a moving picture projecting apparatus forcarrying out my novel method;

Figs. 2 and 3 are a side view and a rear view, respectively, the lampcasing and the film moving device being omitted in the rear VIBW' Fig. 4is an illustration of a film to be used in connection with thisapparatus;

Fig. 5 shows an apparatus for compensating for variations of the lightintensity of the projections;

Fig. 6 illustrates a plan view of a theater room uipped with the novelapparatus;

Fig. is a rear elevation thereof;

F ig. 8 is a diagrammatical representation of an observer properlyseated in the theater and equipped with a nose plece;

Figs. 9 and 10 are diagrams illustrating the perception times ofdifferent lights as difi'erent states of adaption; the times beingrepresented by the ordinates;

Fig. 11 isa diagrammatical representation of the sequence of right-eyeprojections and left-eye projections and the neutralizing lightprojections and of the sequence in which they are perceived by the eyesof .a spectator;

Fig. 12 illustrates a plan view of atheater room equipped with laterallights alternately extinguished and released by rotating shut- Similarcharacters of reference indicate corresponding parts throughout thevarious views. v i

In Fig. 1 the source of light for projecting the pictures on the screenis designated by 1, the light beam magnified by. the reflector- .isintermittently rotated by a one-tooth gear 9 continuously driven withsuch a speed as to impart to the film about 16 motion impulses persecond, each impulse transporting the film by the length of a picture.As such a driving mechanism is well known in the art, a detaileddescription thereof may be dispensed with.

The film 7 contains two rows of pictures, the one row11 (Figs. 3 and 4)representing the right-eye pictures and the other row 11 the left eyepictures, corresponding pictures, i. e., pictures simultaneously taken,being adjacent to, and registering with each other. The size of theictures is preferably so chosen that a film hand of standard width maybe used. In the represented embodiment, the

pictures are rectangularly arranged with respect to the customaryarrangement, a horizontal line represented in a picture extendinglengthwise the film band.

The beam 52 passing the window 5 and the film 7 guided therein isdividedby the two pictures shown in the window into a beam 2 and a beam2.. Each beam is first laterally deflected b a mirror 12, or 12'.respectively (see Fig. 1i, then it is downwardly deflected by a mirror13 or 13 respectively and is finally directed by a mirror 1.4 or 1 1respectively, and projected through a lens set 15;-

various mirrors are so adjusted that the lefteye representation on thescreen of a very '110 or 15 respectively and on the screen. The

remote point is spaced by about 2% inches leftward from therepresentation of the same point in the right-eye picture. In additionto the two beams 2, and 2 a third neutralizing beam 2,, the purpose ofwhich will be explained hereinafter, is projected on the screen inpredetermined intervals. This beam 2-,. (2 is derived from the source 1by a mirror 21 and a reflector 19 and directed to the screen by a lens20, mirrors 12 13 14,. and a lens set 15 Between the lens 20 and themirror 12 a frame 23 provided with a window 22 is arranged, the size ofthe window 22 being such that the beam covers at least the area on thescreen which is occupied by the projections of the pictures. A rotaryshutter comprising two or more discs 24 supbeams gradually, therebypreventing a pro jection from the moving film. The other discs 24: cutoff the beams temporarily while the film is stationary. The purpose ofthis interruption is to diminish the glimmering of the picture. I

A rotating drum-shaped shutter 25 provided with three circumferent-iallydisposed rows of windows 25,, 25, and 25 is so mounted in the apparatusthat said three rows of 7 windows register with the'three beams 2 2,

and 2,, and are intermittently transversed thereb The drum mounted on anaxle 32 is uni ormly driven by a motor 31. The arrangement of themirrors 12,, 12,, 13,, 13,, 1 1,, 14, and the lenses 15,, 15, being soprovided, that the light projections 2 2,, 2,, on the screen 16 areextinguished beginning from one and the same side, if the discs 24 orthe shutter 25 are rotating. Under the condition that the size of theopenings 25,, 25,, 25,, are smaller than the heights of the pictures 1111, or of the window 22, the light projections 2 2,, 2 on the screen 16will appear as small vertical stripes. The manner in which thedisposition of the windows determining the time for which the individualbeams are cut off, is designed will be explained hereinafter.

The theater room (Figs. 6 to 8) is equipped with lamps or other sourcesof visible or invisible (infra-red, ultraviolet) light 51,, 51, whichare arranged on the right and on the left hand side in such a manner asto project light rays in a predetermined direction only. The rays 50,coming from the left hand side are so directed as to. act substantiallyon the left eye only of any properly seated spectator while the rays 50,act only on the right eye. Such an arrangement is rendered possible bythe screening effect of the nose which protects either eye from the rayscoming from the other side as will be seen from Fig. 8.

A nose v53 of average dimensions cuts from the total field of view 55 asmall lateral monocular part 55, or 55, respectively, on either sidewhich is available to one of the eyes 52 and 52, only. As experience hasshown that the spectators do not move their heads while looking at theperformance on the screen 16, the rays 50, or 50, may be sent in anydirection which lies within the limits of the monocular fields of view55 or 55,. In case of an abnormal shape of face which does not providefor sufficiently large mo- 8') as sources of light, mirrors of a smallbreadth nocular fields of view, or in case of spectators seated so farin front that they want to move 1 their heads to better observe theperformance, an artificial nose prolongation member 54 (Figs. 12 and 14)may be used. This member may consist of cardboard and may be attached tothe nose in any suitable manner. The sides of the member may be white orcolored to correspond to the colors of the sources of light 51 51,. Thesources of light arranged on the sides of the theater room maybe formedby incandescent lamps or glowing tubes 51,, 51, as indicated in Fig. 8,or a plurality of mirrors (Fig. 12) receiving light from central sources60, or 60,. In so order to prevent the radiation of light in undesirabledirections, screens 56,, 56, (Fig. may be provided or, in the case ofmirrors may be used and properly adjusted. as

In Figs. 6 and 7 I have shown a theater room in which thesea-ts arearranged in three groups and in concentric arcs so that the heads of thespectators are radially directed towards the screen 16. For each groupof seats an individual group of light rays is pro duced so that eachspectator will receive the side lights under the proper angles andregardless of the group in which he is seated. The left group of seats57 is exclusively exposed to the; rays coming from the source 51 or 51,respectivelyl The central group 57 receives only rays from the source 51or 51, while the group on the right is exclusively exposed to the rayscoming from 109 51 or 51 The arrangement heretofore described may beoperated in various manners. According to the preferred modification ofmy invention the lateral sources of light 51, and 51, 185 deliver lightof different colors or intensity. The source 51 for instance may delivera red light while the source 51, supplies a green light. Various wellknown ways are available for obtaining lights so colored. The 110sources of light may be provided with a colored light filter permittingrays of a certain color only to pass while absorbing all other rays, orthe light beam coming from the source may be divided into itsdifierently colored constituents by means of a prism, whereupon the raysof a certain color are sent into the desired direction, the remainingrays being deflected and finally absorbed by suitable screens.

The difierently colored lights acting on the eye of any observer havethe effect of bringing both eyes into a different state of adaption. Acertain red light such as a projection of a red colored picture willappear darker to the left eye than to the right eye. A green light willhave the reversed effect, appearing brighter to the left eye than to theright one. Another effect of the different state of adaption of botheyes is that the 130 will perceive the same projection 12 at the time7),. green light a which is less intense than the light I) will not beperceived by the eyes before the expiration of the times a and a Fig. 10illustrates the perception times for two different red light projections0 and d 1 which will be perceived by the eyes L and R after theexpiration of c, and 0,- or al and d,

respectively. p i

Fig. 11 illustrates the successive pro ections of the pictures and ofthe neutralizing light in their timed relation. A A A A representprojections of left eyepictures, begin-.

ning at the times 1, 5 and 9 and lasting approximately "for one timeunit. The light beam 2 projecting these pictures is composed of greenrays which may be obtained by means in the manner described inconnection with the colored lights 50, and 50,.

' C1, C C represent projections of right eye pictures beginning at 3, 711 and performed by means of the beam2,, which is red.

B B B and D D D D are projections of the bright neutralizing beam 2.,be-

ginning at the times, 2, 4, 6, 8, 10, 12, 14 and lasting preferably fora somewhat shorter time than the picture projections A A A A and C G 0as will be explained later. The neutralizing projections have adifferent color in alterations, the projections B being green and theprojections D being red. These colors may be obtained by inserting greenand red respectively light filters into alternating windows Theintensity of the beam 2,, is so regulated that the neutralizingprojections are three to four times as bright as the pictureprojections. As a short light projection lasting a certain time isperceived by the eye for a time exceeding the time of the actualprojection by a certain amount which is in proportion to the lightintensity, the relatively strong neutralizing projections being shorterthan the picture projections are nevertheless perceived for the samelength oftime. Fig. 11 indicating. the time and the length of everyprojection forms a basis for the design of the width and the distance ofthe windows 25 25, and 25,. I An example of the sequence andtimeintervals of the projection of the light rays 2 2,, and 2,, is asfollows:

The green left-eye picture image is projected for approximately .0008 ofa second on the screen a time interval of approximately .0002 of asecond in which there is" no projection on the screen follows, then aneutraliz- 111g hght projection of the red color for approximately .0006of a second takes place, followed by a time interval of approximately.0004 of a second in which there is no proj ection, a red right-eyepicture image is then projected for approximately .0008 of a second, atime interval of approximately .0002 of a second in which there is noprojection follows, a neutralizing light projection of the green coloras said right-eye picture image-is projected for approximately .0006 ofa second and actime interval of approximately .0004 of a second in whichthere is no projection completes one cycle. These time intervals can bevaried to suit the projection of pictures and lights of differentintensities.

The effect of these projections on a spectator is as follows: I

The green projection A of a left-eye picture beginning at the time 5will first be perceived by the left-eye after the expiration of a; timeunits, i. e., in therepresented example at the time III. While theactual projection lasts approximately for one time unit, its perceptioncontinues for two units, i. e., till the time IV. This period ofperception by the left eye is indicated by a cross-hatched square in thecolumn marked L in the center of Fig. 11. While the left eye isperceiving the projection A the right eyereceives simultaneously theimpression of the three projections A ,.B and D The. green projection Abeginning at the time 1 is first perceived A,

units later, at the time III and lasts to the time IV. The bright greenprojection B beginning at the time 4, is first perceived 61- unitslater, at the time III and lasts also to the time IV. The bright redprojection D beginning at the time 6, is perceived 41, units later, atthe time III as shown in the diagram. The perception lasts until thetime IV. As the bright projections B and D are much brighter thanthe'picture projection Aand represent themselves simpl as a uniformlylighted area being produced by the neutral-' izing beam 2 they have theheretofore explained effect of extinguishing in the right eye theimpression which otherwise might be created by-the picture projection Awithout interfering, however, with the simultaneous activity of the lefteye. This effect on the right eye is symbolized by a plain square in thecolumn marked R in Fig. 11.

At the time IV, the right eye begins to perceive the red pictureprojection G which follows the neutralizing projection D This receptionperiod lasting from the time IV to the time V is indicated by across-hatched square in the column R. The left eye receivessimultaneously the impression of the projections 0 ,13 and B theprojections D and B representing neutralizing projections whichextinguish any impression that might be created by the projection C Forthe left eye the perception times ofthe projections ression which,however, due to its uniform-" ity, does not interfere with thevisibility of the picture. I have found that the periods during whichpictures are perceived, follow each other without interruption as is thecase in the described example, a spectator will never gain an impressionof blurring of the moving picture which mi ht be'expected from theintermittent neutraizing light projections.

The light intensities for the four different projections and for thelateral lights must be so chosen that the resulting perception time aequals 0 and 6, equals (i I have found that if this condition iscomplied with, the equality of the reception times a and c, as well asof 6 and (Z results coincidentally under the condition that proper tintsof the light colors are used.

In determining the length of time of the various projections, thefollowing phenomenon must be taken in consideration. A short projection,shorter than 1/50.sec., will first be perceived after the expiration ofthe perception time. Some time after this impression which lasts for acertain period has ceased, the eye receives a second impression of theprojection which has the color and about the same intensity as the firstimpression and which lasts'approximately the same length of time. Theinterval between the two successive impressions created by the samelight projection is known as the dark interval. The succession andlength of the various projections A, B, C and I) must be so chosen thatan impression created by a picture projection is perceived during thedark interval which follows the impression of the preceding neutralizingprojection. Unless this condition is complied with the picture will notclearly be perceived owing to the interfering second perception of theneutralizing projection.

' As the perception times a; and e of the picture projections dependupon the light; intensity thereof, they will vary if=theilight.:

intensity varies'as may be the case if the movie picture shows insuccession, for instance, bright landscapes and dark streets.

In order to compensate for such variations, the intensity of the laterallights is preferably .varied in correspondence with the variations ofthe picture projections, whereby the absolute length of the percep tiontimes is kept constant. The means for varying the lateral lights will bedescribed hereinafter. If a, series of particularly bright pictureprojections will occur in the performance, which have the tendency ofbeing prematurely perceived by an observer, the intensity of the laterallights is correspondingly magnified whereby the sensibility of theobservrs eyes s diminished to a certain degree. The perception time,consequently, will be kept unvaried. In order to avoida change in theperception times of the neutralizing projections, the intensity of thesame is also varied in correspondence with variations of the pictureprojections.

The control of the intensity of the lateral lights and of theneutralizin light beam 2,, may be automatically per ormed by themechanism illustrated in Fig. 5; 43 represents a-movable transparentplate or screen, the transparency of which decreases gradually' from oneend towards the other. This plate is arranged in front of the source oflight to be controlled as the source 2 or the lateral lights. Bydisplacing the screen 43 any desired percentage of the light may beabsorbed. The screen 43 is attached to the is subjected to the action oftwo electromagnets 49 which may be energized by a current supplied bythe line 41. By means of reflectors 35 (Fig. 2) and 37 and of a lens 36,a light beam 34 is thrown through the window 38 (Fig. 3) past which thefilm is running. Behind the window 38 a mirror 39 is placed, reflectingthe light beam into a photoelectric element 40, sensitive to variationsof radiatiofi. are well known, a description thereof may be dispensedwith. The change of the radiation directed on the electro-opticalelement causes a corresponding variation in an electrical currentconducted therethrough. The electrical current is conducted to amagnifying apparatus 42 (Fig. 2) and the magnified current is suppliedto the magnets 49. When the radiation directed on the element 40increases, owing, for instance, to the occurrence of a series ofparticularly bright pictures in the film, the energization of themagnets 49 is changed and the screen 43 is moved by action of the weight47 to increase the intensity of the controlled light. As the adjustmentof the screen 43 takes some time, the window 38 is so far spaced fromthe window 5 that the adjustment initiated b a certain picture passingthe window 38 wil have been completed when said picture reaches thewindow 5 and is then projected.

Instead of varying the lateral lights 50 50., according to thebrightness of the picture projections 2 As such elements 2,, and theneutralizing t the same percentage, the absolute lengthsperformed by thecurrent of the photo-electric element 40 affecting the revolutions ofthe motor 31 in the usual manner.

A third Way is keeping the intensityof the picture projections 2 2,constant, as for varying the neutralizing light 2 and the lateral lights50,, 50, and the speed of the shutter 25 is not necessar As it ispossible that the left-e e and rig t-eye picture have a differingrightness, .two transparent screens 43,, 43, (Fig. 15) are required forregulating theleft and right light beam 2 2,. The transparent screensare operated by the current ofthe elements 40 40,, which are induced bythe respective li ht beams 34;, 34,, passing through the le -eye andright-eye picture of the film 7 and being thrown by the mirrors 39,, 39,into the elements 40 40,. If for instance the new series of pictures areshowing a greater brightness, the transparent screens 43,, 4:3, diminishthe intensity of the light beams 2 2, in such a manner, that the lengthsof the respective perception times do not vary.

As mentioned above, the critical'state of two different colors beingobtained by creating two certain states of adaptation only by varyingthe intensity of the lateral lights 50,, 50,, these light rays may havethe same color but must be of a different intensity- In respect of thediagrams Figs. 9-11, where the light projections A and B may be of abluish color, the right lateral light rays 50, must be of a greaterintensity than the left ones 50,. The left lateral lights may be removed, if the diffused light-0f the theaterroom is sufficient, to bringthe left eye in the certain state of adaptation.

Another way .of creating a different state of adaptation is by wearingcolored glasses, (7 0,, 7 0,, Fig. 16) supplied with central lookingholes. The margins of the glasses being of a different color ortransparence, the light passing through creates the required differingstates ofadaptation of the left and right eye. By wearing those marginalglasses, the screen vcan be seen clearly while the eyes are protectedfrom theusual lights in the theater.

Another arrangement concerning the invention is as follows:

The left-eye and right-eye picture projections 2 2, are thrown inalternation upon the screen 16 by means of the rotating shutter 25 (Fig.12). The neutralizing light 271. is removed. The lateral lights 51,,51,, which are extinguished and released by rotating shutters 63 63,(Fig. 13) in synchronism to the picture projections 2 2,. The shuttersmounted on axis 64 64, are driven by small ,alternating current'motors65 65, and running in synchronism to the motor 31. As

soonas a left "eye picture projection 2 is appearing on the screen 16,the left lateral light 50 is extinguished by the shutter 63,

and the right lateral light 50, is released by the shutter63,. The beamof the right lat the picture projection on the screen 16. But' beingilluminated by the lateral light, the wing is throwing such a strong,homogene neutralizing light into the eye, that an impression of apicture projection on the screen 16 is impossible; By turning the wings66,, 66, in the joints 68 68,, each observer may regulate the intensityof the lateral light beams 50,, 50, at will. Choosing the period of thealternation of the left-eye and righteye picture projections with regardto the dark interval it is evident that a threedimensional impression ofthe moving pictures may be attained.

By way of example, I show in Fig. 17, by diagrammatic plan, anarrangement of means or apparatus whereby to extinguish and releasealternately the lights on the side of the connection with thedrum-shaped shutter 25 is a shaft 32. The shutter 63 at the lefthandside is operated from the shaft 32 A through the cooperating bevel gears7 5 7 6,,

shaft 77 and cooperating bevel gears 78,,

7 9,. The shutter 63,, at the right-hand side is operated from shaft 32through the 00- h operatingbevel gears 75,, 76,, shaft 77 ,,-and

cooperating bevel gears 7 8,, 79,. The shutters 63,, 63, having twoopaque sections are rotated four times as fast as the shutter 25,

which has eight openings 25 25, in each row. 7

The principles of stereoptical seeing are well known and need,therefore, 'no detailed discussion. v

Figs. 6 and 12 illustrate diagrammatically the effect of a left-eyepicture and ofa right-- eyepicture of an observer. The points 17 and 17,or 18 and 18, represent the ill-ustration of a certain object in theleft-eye picture or the right-eye picture respectively. While these twopictures are represented as being simultaneously projected on thescreen, it must be kept in mind that their projections are performed insuccession, the succession being so quick, however, that an observerwill notbecome aware thereof but will have the same impression as thatwhich a simultaneous presentation to the eyes would create. The objectshown in 17 or 17, respectively, will appear to the spectator to beinfinitely remote. Another object shown in 18 or 18, respectively, willappear to be located in the point 18. x

Instead of red and green colors for the- 5 lateral lights 51 51 and forthe beams 2 2, and 2 other colors or color compositions may be used. Asa mixture of complementary colors results in white or grey, theimpression created by the successive projections will substantiallyequal that which would be created by the use of uncolored lights.

If the left-eye pictures and right-eye pictures are taken throughred-yellow filters I and green-blue filters respectively and areprojected in the corresponding colors later on the pictures will appearin natural colors.

Various changes in the heretofore described arrangement and method maybe made with out departing from the spirit of the invention.

I claim:

1. The method of producing stereoscopi pictures which comprisesproducing light 0;.5 different wave lengths for each eye, so as to bringthe eyes into different states of adaptation forming right and leftimages with suflicient rapidity to produce persistence of vision, anddirecting into each eye of the observer a beam of light neutralizing theimage which that eye should not see.

2. The method of producing stereoscopic pictures-which comprisesproducing light of difierent intensities and different wave lengths foreach eye, so as to bring the eyes into different states of adaptation,forming right and left images with sufiicient rapidity to producepersistence of vision, and direct-. ing into each eye of the observer abeam of light neutralizing the image which that eye f should not see.

3. The method of producing stereoscopic pictures which comprisesproducing light of different wave lengths for each eye, so as to bringthe eyes into different states of adaptation, formin right and leftimages with suflicient rapidity to produce persistence of vision, anddirecting into each eye of the observer a beam of light neutralizing theimage which that eye should not see, said first mentioned images beingformed in the dark intervals between the directing of the beams of lightinto the eyes. i 4:. The method of producing stereoscopic picturescomprising forming right and left images with sufficient rapidity toproduce persistence of vision, directing into each eye of the observer.a beam of light neutralizing the images which that eye should not see,and varying the intensity of the neutralizing beam of light in relationto the brightness of the images.

In testimony that I claim the foregoing as my invention, I have signedmy name hereto.

NEWTON ARFSTEN.

